The present invention relates to the offshore petroleum industry, and it relates more particularly to systems for connecting submerged fluid-transporting lines (all types of xe2x80x9crisersxe2x80x9d) to floating supports (of the following types: floating production, storage and offloading (FPSO) unit; tension leg platform (TLP), submersible pipe-alignment rig (SPAR), buoy, etc.).
FIG. 7 is a very diagrammatic view of a portion of an offshore petroleum installation. A floating production, storage and offloading (FPSO) unit, referenced 10, is in general disposed immediately above the oil or gas field to be tapped. Tubular structures 12 or xe2x80x9crisersxe2x80x9d connect the various well heads 14 of the field to the floating support. Rigid offloading lines lead away from this floating unit (e.g. the transport line 16) for offloading the petroleum fluid to tanker ships (not shown) for transporting it. For safety reasons, these tankers are relatively far away from the floating unit 10 and the coupling between the unit and a tanker thus goes via a relay mooring constituted by a semi-submerged buoy 18.
Because the positioning of the FPSO unit and of the buoy can vary, in particular in the presence of heavy swell (horizontal variations over a distance of 150 meters (m) are then common), the various connections connecting the risers and transport lines to the FPSO unit or to the buoy must offer a certain amount of flexibility. U.S. Pat. No. 4,943,188 and U.S. 4,907,914 show hinged means that are well suited to riser connections.
However, and as shown very diagrammatically in FIG. 6, an offloading line 16 for transporting petroleum fluid is currently hooked up to the FPSO unit 10 by means of two pulling lines 20, 22 fixed to one end of the transport line and that need to be displaced in two different directions (by means of respective winches 24, 26) so that the transport line 16 can be hooked up exactly to cradle receptacles 28 carried by the FPSO unit.
Unfortunately, such a traditional hooking-up principle is particularly difficult to implement in an installation at sea. In addition, possible interference between the pulling lines and the installations of the FPSO unit or the anchor chains of said unit does not facilitate such hooking-up.
An object of the present invention is to mitigate the above-mentioned drawbacks by proposing a connection system that is particularly easy to install. Another object of the invention is to obtain a system that is reliable over time. Yet another object of the invention is to provide a system that can operate regardless of the type of transport line used.
These objects are achieved by a connection device for connecting a submerged tubular structure to a floating support structure, said connection device comprising a first tubular connection element and a second tubular connection element concentric with said first element, the connection elements being connected respectively to one end of the submerged tubular structure, and to the floating support structure, wherein, with said first tubular connection element being provided firstly with a first shoulder serving to cooperate with a corresponding first abutment face of said second tubular connection element to form a first axial abutment in a pulling direction (T) in which the submerged tubular structure is pulled, and secondly with a second shoulder serving to co-operate with a corresponding second abutment face of said second tubular connection element to form a second axial abutment in a direction opposite from said pulling direction (T), said connection device further comprises locking and tensioning means mounted between said first and second tubular connection elements to act, by putting said first and second shoulders simultaneously in contact with said first and second abutment faces, to provide coupling with zero axial clearance between said two connection elements.
With this particular structure, a single pulling line suffices to install a fluid-transporting line (the submerged tubular structure), the locking means guaranteeing that the forces are distributed as a function of the dynamic loads between the floating support structure and the transport line.
Preferably, the locking and tensioning means comprise at least one actuator secured to said floating support structure. The actuator is mounted to pivot on said second tubular connection element about a hinge axis and against the effect of a return spring surrounding said pin, so as to enable said first tubular connection element to be snap-fastened onto said second tubular connection element.
In order to guarantee tensioning of the coupling over time, the locking and tensioning means further comprise at least one stay put in place at zero clearance and at a predetermined tensioning force by replacing said at least one actuator.
Advantageously, the locking and tensioning means comprise a plurality of actuators distributed uniformly about the second tubular connection element, a stay being disposed between each actuator.
In a preferred embodiment, the first tubular connection element is connected to the end of the submerged tubular structure via hinge means. The hinge means advantageously comprise at least one spherical laminated abutment.